The present invention relates to a head suspension for supporting a head slider of a disk apparatus, and more particularly to a structure to mount a head IC to a head suspension, to suppress vibration.
With increases in the frequency of signals processed by information processing apparatus, disk drive devices must raise the frequency of signals written to a disk medium above the current 70 MHZ, for example, up to 200 to 300 MHZ. In order to raise the frequency of the signals, inductance and static capacitance of the signal line for transmitting the signal between the head slider and head IC must be lowered. For this purpose, the distance between the head IC and head slider can be reduced, to shorten the length of the signal line between these elements.
FIG. 1(a), FIG. 1(b) and FIG. 1(c) illustrate head suspensions of the related art. A head suspension 1 has a head slider 3 at one end part, having an electromagnetic conversion element to write or read information to or from a magnetic disk (not illustrated). Moreover, on the same surface as the surface where the head slider 3 of the head suspension 1 is mounted, a head IC 2 is mounted. The head IC 2 is mounted in the area between the base end and the head slider 3.
As explained above, in the related art, the distance between the head IC and head slider has been reduced by mounting the head IC close to the head suspension. As a result, wiring capacitance and inductance of the signal leads between the head IC and head slider can be reduced so transmission of high frequency signals is possible.
Moreover, as illustrated in FIG. 1(b), the head IC 2 is mounted on the head suspension 1 by a solder bump or gold bump 90 or the like, but an under-fill material 4 is provided between the head IC 2 and head suspension 1 so that the head IC 2 does not float. The under-fill material 4 plays a role of protecting the head IC 2 and bonding to the suspension 1. This under-fill material is injected from a gap between the head suspension 1 and head IC 2 from one side surface of the head IC 2.
In the related art, since the under-fill material 4 is injected from the side surface of the head IC 2, the under-fill material 4 is non-symmetrically distributed in both sides of the center line 5 of the suspension 4, as illustrated in FIG. 1(c). As a result, the load in one side of the center line 5 does not match the load in the other side of the center line 5, and thereby the suspension 1 is twisted. Twisting of the suspension 1 adversely influences the floating characteristic of the head slider 2.
Therefore, it is a first object of the present invention to enable high frequency transmission of signals for a head slider.
A second object of the present invention is to shorten the length of wiring between the head slider and head IC.
A third object of the present invention to acquire the stable floating of the head slider.
A fourth object of the present invention to simplify the mounting of the head IC and reduce manufacturing cost.
In the present invention, since the head slider and head IC are formed on the head suspension, the length of wiring between these elements is short and the signal can be transmitted at a higher frequency. The head suspension is provided with a through hole at the surface for mounting the IC head, so that under-fill material can be injected to the area between the head IC and head mounting surface via the through hole, from the surface opposed to the surface where the IC head is mounted. Thereby, the under-fill material equally spreads on the suspension around the through hole, and a load is equally applied to both sides of the center line of the head suspension. As a result, the head suspension is not twisted and stable floating of the head slider can be assured.
Moreover, fluctuation of the spreading of under-fill material can be controlled, in comparison with injection of a large amount of under-fill material through only one through hole, by forming a plurality of through holes at a plurality of positions. If the plurality of through holes are formed symmetrically on both sides of the center line in the longitudinal direction of head suspension, the under-fill material is distributed equally to the right and left sides of the center line of the head suspension in the longitudinal direction, and twisting of the head suspension can effectively be prevented.
Moreover, a head suspension having a plurality of laminated plate members has been developed to increase its strength. Such head suspensions can be provided with a through hole at each plate member, so that the under-fill can be injected easily, and efficiency of the assembling work can also be improved.